Combined Restricted Stock Units Activity (Detail) - RSUs - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Number of shares
Nonvested as of January 1, 2015	1,718
Granted	1,868
Vested	(662)
Forfeited	(317)
Nonvested as of December 31, 2015	2,607	1,718
Expected to vest as of December 31, 2015	1,970
Weighted average grant date fair value
Nonvested as of January 1, 2015	$ 18.90
Granted	20.49	$ 19.88	$ 16.06
Vested	18.72
Forfeited	19.36
Nonvested as of December 31, 2015	20.03	$ 18.90
Expected to vest as of December 31, 2015	$ 20.03
Aggregate Intrinsic value
Nonvested as of December 31, 2015	$ 56,695
Expected to vest as of December 31, 2015	$ 54,169